The invention relates in general to skeletal stabilization systems, and in particular to implants, surgical guides, delivery instruments and methods for delivering and attaching implants to bony structures such as a vertebrae.
The human spine is a complex structure designed to achieve a myriad of tasks, many of them of a complex kinematic nature. The spinal vertebrae allow the spine to flex in three axes of movement relative to the portion of the spine in motion. These axes include the horizontal (i.e., bending either forward/anterior or aft/posterior), roll (i.e., lateral bending to either left or right side), and rotation (i.e., twisting of the shoulders relative to the pelvis).
The intervertebral spacing (e.g., between neighboring vertebrae) in a healthy spine is maintained by a compressible and somewhat elastic disc. The disc serves to enable the spine to move about the various axes of rotation and through the various arcs and movements required for normal mobility. The elasticity of the disc maintains the spacing between the vertebrae during flexion and lateral bending of the spine, allowing room or clearance for compression of neighboring vertebrae. In addition, the disc enables relative rotation about the vertical axis of neighboring vertebrae, allowing for the twisting of the shoulders relative to the hips and pelvis. The clearance between neighboring vertebrae, as maintained by a healthy disc, is also important to allow the nerves from the spinal cord to extend out from the spine, e.g., between neighboring vertebrae, without being squeezed or impinged by the adjacent vertebrae.
In situations (e.g., based upon injury or otherwise) where a disc is not functioning properly, the inter-vertebral disc tends to compress, and in doing so pressure is exerted on nerves extending from the spinal cord by the reduced inter-vertebral spacing. Various other types of nerve problems may be experienced in the spine, such as exiting nerve root compression in neural foramen, passing nerve root compression, and enervated annulus (i.e., where nerves grow into a cracked/compromised annulus, causing pain every time the disc/annulus is compressed), as examples. Many medical procedures have been devised to alleviate such nerve compression and the pain that results from the nerve pressure. Many of these procedures revolve around attempts to prevent the vertebrae from moving too close to each other by surgically removing an improperly functioning disc and replacing it with a lumbar interbody fusion device or spacer. Although prior interbody devices, including spacers, may be effective at improving the condition of a patient, the vertebrae of the spine, body organs, the spinal cord, other nerves, and other adjacent bodily structures make it difficult to obtain surgical access to the locations between the vertebrae where the spacer is to be installed.
PLIF is an acronym for Posterior Lumbar Interbody Fusion. PLIF is a surgical procedure that may be used to treat the conditions mentioned above. In this procedure, a spacer or implant, bone graft, or a bone graft substitute, may be placed between vertebrae to fuse them and create more stable spine. The bone graft is inserted into the disc space from the back (posterior). In addition, spinal instrumentation such as screws and rods may be used to hold the spine in position and help promote successful fusion. ALIF stands for Anterior Lumbar Interbody Fusion. ALIF is a surgical procedure similar to PLIF, but it is done from the front (anterior) of the body, usually through an incision in the lower abdominal area or on the side. The incision may involve cutting through, and later repairing, the muscles in the lower abdomen. In recent years, surgeons have begun to use a TLIF procedure (Transforaminal Lumbar Interbody Fusion). A TLIF may accomplish the same goals as a PLIF procedure, however in the TLIF technique the bone graft or implant in inserted into the disc space laterally or from the side. The TLIF technique usually results in the nerve roots being moved less during the procedure, as compared to a PLIF, and may reduce the risk of scarring or damaging the nerve roots. XLIF stands for extreme Lateral Interbody Fusion. XLIF is also a relatively new surgical procedure and avoids an incision that traverses the abdomen and also avoids cutting or disrupting the muscles of the back. In surgical procedure, the disk space is accessed from a very small incision on the patient's side. The bone graft or implant may then be inserted into the disc space laterally or from the side.